The overarching goal of this Research Center is to examine the reading disabilities (RDs) present in children grades 3-8, including classification, identification, treatment, prevalence, neurocognitive characteristics, as well as the influence of comorbidities (Attention Deficit Hyperactivity Disorder;ADHD) on reading. While much is known about early reading development and disorders, there has been much less examination of reading and RDs past the early elementary grades. Therefore, there is a critical gap in knowledge about what it takes for a reader to be able to effectively glean information - or learn - from text, even though this is arguably the most important skill needed to achieve academic success after the 3rd grade. Our Research Center seeks to fill this critical gap in knowledge by bringing together a diverse and talented set of researchers and institutions (Kennedy Krieger Institute, Haskins Laboratories, Educational Testing Services (ETS), and University of Maryland) to conduct inter-related projects, the findings from which will allow us to gain a deep understanding of the neurobiological and behavioral processes that influence reading achievement past the early elementary grades. Our overarching hypothesis is that RDs past the early elementary years are heterogeneous in nature, caused by both "bottom up" and "top down" processes. Within this context, we propose projects that I) examine the neurobiological and behavioral development of word level efficiency, the relationship between word-level and text-level fluency and comprehension, and the influence of different textual demands upon comprehension;II) examine the validity of RTI as a way of identifying children with RDs, and to determine if there are neurocognitive indicators that predict intervention responsiveness;III) determine how the cognitive aspects of ADHD (processing speed, working memory) influence reading comprehension;and IV) to determine the prevalence of different subtypes of RDs by building upon the knowledge gained from Projects I, II, and III, as well as analyses of extant datasets. Thus, within the framework of Project IV, the projects of the Research Center converge in an endeavor that will have significant public health value. Knowing the common subtypes of RDs at what age, as well as the influence of ADHD, will help reveal what the instructional emphasis (es) should be for the older children in our nation, including what risk factors teachers should be looking for.